EP1223585B1 - Tri-layer stack spin polarised magnetic device and memory using the same - Google Patents
Tri-layer stack spin polarised magnetic device and memory using the same Download PDFInfo
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- EP1223585B1 EP1223585B1 EP01403132A EP01403132A EP1223585B1 EP 1223585 B1 EP1223585 B1 EP 1223585B1 EP 01403132 A EP01403132 A EP 01403132A EP 01403132 A EP01403132 A EP 01403132A EP 1223585 B1 EP1223585 B1 EP 1223585B1
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Images
Classifications
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- H10B61/20—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having three or more electrodes, e.g. transistors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/161—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/165—Auxiliary circuits
- G11C11/1675—Writing or programming circuits or methods
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
- H01F10/3218—Exchange coupling of magnetic films via an antiferromagnetic interface
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
- H01F10/324—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer
- H01F10/3254—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
- H01F10/324—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer
- H01F10/3268—Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer the exchange coupling being asymmetric, e.g. by use of additional pinning, by using antiferromagnetic or ferromagnetic coupling interface, i.e. so-called spin-valve [SV] structure, e.g. NiFe/Cu/NiFe/FeMn
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N50/00—Galvanomagnetic devices
- H10N50/10—Magnetoresistive devices
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
- Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree
Definitions
- the present invention relates to a magnetic device spin polarization and stack (s) tri-layer (s) and a memory using this device.
- MRAM Magnetic Random Access Memory
- magnetic memory direct access or random
- MRAM magnetic memories have been renewed with the development of magnetic tunnel junctions (abbreviated MTJ for "Magnetic Tunnel Junction”) with a high magnetoresistance at room temperature.
- MTJ magnetic tunnel junction
- FIGS 1A and 1B annexed schematically illustrate the structure and function of such a junction.
- the junction bears the reference 2. It is a stack comprising an oxide layer sandwiched between two magnetic layers. This system functions as a spin valve, with the difference that the current flows perpendicular to the plane of the layers.
- One of the magnetic layers is called “free” because its magnetization can be oriented in an external magnetic field (bidirectional arrow); the other is said “trapped” because its direction of magnetization is fixed by an antiferromagnetic exchange layer (unidirectional arrow).
- the magnetizations of the magnetic layers are antiparallel, the strength of the junction is high; when the magnetizations are parallel, the resistance becomes weak.
- the relative variation of resistance between these two states can reach 40% by an appropriate choice of materials.
- junction 2 is placed between a switching transistor 4 and a current supply line 6. A current flowing in it produces a magnetic field 7.
- a conductor 8 orthogonal to the current supply line 6 (c) that is to say in this case, perpendicular to the plane of the figure) makes it possible to produce a second magnetic field 9 (located in the plane of the figure).
- the transistor 4 In the "write" mode ( Fig. 1A ), the transistor 4 is blocked. Currents flow in the current supply 6 and in the conductor 8. The junction 2 is therefore subjected to two orthogonal magnetic fields. One is applied along the axis of difficult magnetization of the free layer, in order to reduce its reversal field, the other being applied along its easy axis in order to cause the reversal of the magnetization and the writing of the memory point . In principle, only the memory point placed at the intersection of the two lines 6 and 8 is likely to turn over, because each magnetic field taken individually is not large enough to cause a tilting of the magnetization.
- the transistor In the "reading" mode ( Fig. 1B ), the transistor is placed in saturated mode (that is to say that the current passing through it is maximum) by sending a positive current pulse in the base.
- the current sent in line 6 passes only the memory point whose transistor is open. This current makes it possible to measure the resistance of the junction. By comparison with a reference memory point, the state of the memory point ("O" or "1") can thus be determined.
- the present invention precisely aims to overcome these disadvantages.
- US-A-5,966,323 describes a low-field magneto-resistive tunnel junction for high-density networks.
- EP-A-1,187,103 discloses a magnetoresistive effect device and a memory using this device.
- the invention aims to reduce the critical current density from which the reversal of magnetization occurs in the free layer.
- the work and reflections of the Applicant made it possible to understand that this critical density was linked to the demagnetizing field specific to the free layer.
- the invention proposes a device in which this demagnetizing field is very weak or even zero.
- a three-layer stack hereinafter referred to as a "tri-layer stack” or simply a "tri-layer” layer
- thickness sufficiently low that the coupling between the two magnetic layers is strong enough that the magnetizations in these layers are antiparallel. Overall, such a system does not present (or little) demagnetizing field.
- the Applicant qualifies such stacks as "synthetic".
- the invention therefore relates to a magnetic device according to claim 1.
- the trapped layer is also constituted by a tri-layer stack, this second stack being covered with an antiferromagnetic exchange layer fixing the direction of the magnetizations in said second tri-layer stack.
- the device comprises a third tri-layer stack separated from the first by a non-magnetic conductive layer, this third tri-layer stack resting on a second antiferromagnetic exchange layer fixing the magnetizations in this third tri-layer .
- the material of the magnetic layers of the first and / or second and / or the third stack is preferably of a material selected from the group consisting of Co, Fe, Ni and their alloys.
- the non-magnetic conductive layer of the first and / or second and / or third trilayer stack is preferably a metal selected from the group consisting of Ru, Re, Cu, Cr, Pt, Ag.
- the first and / or second antiferromagnetic layer may be an Mn-based alloy (for example FeMn, IrMn, NiMn, PtMn, PtPdMn, RuRhMn).
- Mn-based alloy for example FeMn, IrMn, NiMn, PtMn, PtPdMn, RuRhMn.
- An electric current flowing in a conductor consists of electrons whose spin has no reason a priori to be oriented in a particular direction.
- this current passes through a magnetic layer having a particular magnetization, the spins will be oriented by magnetic moment exchange phenomena, so that the electrons will emerge from this layer with a polarized spin.
- a layer or a set of such layers
- This phenomenon can play both in transmission (through the layer) and in reflection (on this layer), depending on the flow direction of the current. It can also act in the opposite direction by preferably passing electrons having a polarized spin in a certain direction.
- the function of the layer is that of an analyzer.
- the first embodiment of the invention consists in using a tunnel junction formed of two tri-layer stacks disposed on either side of an insulating layer, for example alumina (Al 2 O 3 ).
- an insulating layer for example alumina (Al 2 O 3 ).
- One of the three-layers has its magnetization direction fixed by exchange coupling with an antiferromagnetic layer.
- This layer plays a dual role of polarizer (writing) and parser (writing and reading).
- the choice of a tri-layer was chosen to eliminate the magnetostatic coupling with the second tri-layer and thus to be able to use the memory without an external compensating field.
- the other tri-layer is free to orient itself in the spin polarization direction.
- This layer has a planar anisotropy defining an easy axis and a hard magnetization axis in order to reduce the write time.
- the thicknesses of the magnetic layers of this tri-layer system are almost equal in order to eliminate the demagnetizing field effect and thus allow the magnetization of this layer to precede easily out of the plane.
- a current of density greater than the critical density crossing the junction will cause precession and alignment of the magnetization of the free layer (closest to the oxide barrier) by transfer of the magnetic moment of the electrons polarized at the magnetic moment of the free layer.
- the voltage appearing at the terminals of the junction makes it possible to follow the magnetic state of the free layer.
- the writing can be done in direct current or in pulsed current, the duration of the pulse to be adjusted according to the process of reversal of the magnetization.
- a current of density less than the critical density crosses the junction and makes it possible to read the magnetic state of the device, which thus behaves like a memory point.
- the device comprises two tri-layer (or “synthetic") stacks, respectively 12 and 16, one for the trapped layer (12) and the other for the free layer (16).
- the device comprises successively, from top to bottom, an antiferromagnetic exchange layer 10, the trapped layer 12, a non-magnetic insulating layer 14, the free layer 16, the assembly referenced 18 forming a magnetic tunnel junction .
- This junction rests on a conductive substrate 20 and is interposed between a conductor 22 and a transistor 24.
- the trapped layer 12 is a tri-layer composed of two magnetic layers 121, 123 separated by a non-magnetic conductive layer 122.
- the free layer 16 is a tri-layer composed of two magnetic layers 161, 163 separated by a non-magnetic conductive layer 162.
- the magnetizations of the two magnetic layers are antiparallel, as represented symbolically in the figure by the arrows of alternating directions, arrows which represent the magnetization.
- This antiparallelism is due to a very strong antiferromagnetic coupling existing between the magnetic layers.
- the thicknesses of the magnetic layers 121, 123 are advantageously the same in order to have a zero magnetostatic coupling on the free layer 16.
- the free layer 16 has characteristics similar to the trapped layer 12. However, not being trapped by exchange, it is free, and sees the direction of its magnetization change when a spin polarized current passes through it. This change is related to the transfer of magnetic moment of the electrons towards the magnetization of the layer.
- the barrier 14 is preferably formed of an oxidized or nitrided aluminum layer, and is obtained by methods known to those skilled in the art (plasma oxidation, natural oxidation in situ, atomic oxygen source,. ..). Semiconductor materials may also be employed but the magnetoresistive properties are not as good as with nitrides and oxides.
- FIG. 3A illustrates the writing of an "O" and FIG. 3B the writing of a "1".
- the current supply and the transistor have not been shown.
- the different directions are marked with respect to a trirectangular trihedron Oxyz, the direction Oz being perpendicular to the plane of the layers.
- the Figure 4A shows how the component My of the magnetization of the layer 161 changes sign and the Figure 4B shows the oscillation of the Mz component during the precession movement that accompanies the reversal of the magnetization.
- a current (continuous or pulsed) of positive sign that is to say circulating from top to bottom (hence to the transistor) is circulated in the stack.
- the electrons see their spin polarized in the layer 123 in the direction (-y). They will transmit their magnetic moment to the moments of the layer 161 whose magnetization will align parallel to that of the layer 123.
- the magnetization of the layer 161 will precede around the axis (-y) with a component Mz that will oscillate over time, as shown in FIG. Figure 4B .
- the angle of the precession cone exceeds 90 °, the direction of rotation will reverse and the magnetization will realign according to (+ y).
- the number of precessions required for the reversal depends on the anisotropy of the layer in its plane.
- the anisotropy is weak (curves 30 and 32)
- the inversion requires a large number of oscillations of precessions but a weak critical current.
- the turning time is shorter but a stronger current is needed to overcome the anisotropy.
- the writing can be done in direct current or pulsed.
- pulsed current the duration of the pulse must be long enough for the reversal to be complete.
- the overturn control can be done by measuring the voltage across the junction. When the magnetizations of the layers 123 and 161 are parallel, the Electron transfer probability by tunnel effect is high and the resistance of the junction is low. If the flipping did not occur completely, the resistance is great. In comparison with the voltage taken at the terminals of a reference junction, the magnetic state of the device is determined. In this magnetic state control step, the 123 (exchange-fixed) layer acts as an analyzer to probe the orientation of the free layer 161.
- a current of negative sign is circulated as shown in FIG. 3B.
- the polarized majority electrons in the layer 161 according to (-y) will cross the layer 123, while the minority electrons polarized according to (+ y) will accumulate in front of the layer 123.
- Antiparallel spin electrons at layer 161 will transfer their magnetic moment to the moments of layer 41 and cause a precession until the magnetization of layer 161 reverses as shown in FIG. 3B.
- This magnetic configuration corresponds to the writing of a "1" and the resistance of the junction is maximum.
- a current whose density is less than the critical density is sent and the output voltage is compared with the voltage of a reference junction, in order to determine the magnetic state of the device.
- the device comprises three tri-layers, two of the tri-layers being disposed on either side of an insulating layer, by example alumina (Al 2 O 3 ).
- an insulating layer by example alumina (Al 2 O 3 ).
- One of these tri-layers has its magnetization directions fixed by exchange coupling with an antiferromagnetic layer. This layer plays a dual role of polarizer (writing) and parser (writing and reading).
- the choice of a tri-layer makes it possible to eliminate the magnetostatic coupling on the second tri-layer and thus to be able to use the memory without an external compensating field.
- the other tri-layer is free to orient itself in the direction of polarization of the spins.
- This layer may have a planar anisotropy defining an easy axis and a hard magnetization axis in order to reduce the write time.
- the thicknesses of the magnetic layers of this system are almost equal in order to eliminate the demagnetizing field effect.
- the device also comprises a polarizer separated from the tunnel junction by a non-magnetic conductive layer and preferably formed of a tri-layer stack trapped by exchange with an antiferromagnetic layer in order to maintain its direction of magnetization.
- the figure 5 illustrates this second embodiment.
- the three tri-layers bear respectively the references 16, 12 and 32.
- the third tri-layer 32 is separated from the first 16 by a non-magnetic conductive layer 30.
- This third tri-layer comprises two magnetic layers 321, 323 separated by a layer non-magnetic conductor 322. It is based on an antiferromagnetic coupling layer 34 which fixes the magnetization in the layer 323, therefore in the layer 321.
- the third tri-layer 32 is thus of the trapped type, like the second (12).
- the assembly rests on a conductive substrate 36.
- the layer 30 separating the first and third tri-layers may be formed from a noble metal. Its thickness is chosen between 3 and 10 nm to avoid inadvertent magnetic couplings between the tri-layers 16 and 32.
- the writing of the magnetic states "1" and “O” is effected, as before, by the choice of the orientation of the direction of the current as shown by the Figures 6A and 6B .
- the addition of the third tri-layer 32 will stabilize the magnetic states and thus reduce the critical current density by a factor of 2.
- the current biased in the curve 123 according to (-y) (with respect to the same Oxyz trirectangeal trihedron not shown) will cause the alignment of the layer 161 by transfer of the moment of the electrons to the magnetization of the layer 161.
- the electrons are always polarized along (-y) and polarize according to (+ y) after passing through the layer 163, without causing the layer 163 to tilt because of the antiferromagnetic exchange between the layers 161 and 163 which is much higher than the coupling exerted by the electrons.
- the polarizer 32 eliminates the magneto-static coupling field on the layer 16 and also makes it possible to have an identical direction of exchange between the layers 121 and 323 in order to make possible the magnetic ordering of the antiferromagnetic exchange layers 10 and 34. It is indeed difficult to define two opposite directions of exchange in a system using a single type of antiferromagnetic material.
- the reading is performed as in the first variant by injecting a current of density less than the critical density and comparing the voltage read to the voltage of a reference junction.
- Mode of realization 1 2 t (nm) 5 5 Ms (emu / cc) 1500 1500 Effective Hk (G) 40 40 JC (writing) (A / cm 2 ) 3,2E + 05 1.6E + 05 RA max (Ohm. ⁇ m 2 ) 188 375 Jc (reading) (A / cm 2 ) 1.6E + 05 8E + 04 a min (micron) 0.12 0.12
- Such RA products can be obtained either by plasma oxidation or, preferably, by natural oxidation in situ.
- the figure 7 finally, shows a memory formed of a matrix of memory points addressable by rows and columns.
- Each memory point comprises a device according to the invention, with a stack of layers symbolized by a resistor 60 and a switching means 70 constituted by a transistor.
- Each stack is connected to an address line 80 and the base (or gate) of the transistor to an address column 90.
- the lines 80 are called “bit lines” and the columns 90 "word lines” (or digit).
- the lines 80 are connected to the outputs of a line addressing circuit 85 and the columns 90 to the outputs of a column addressing circuit 95.
- a reference column 100 which allows reading.
- the reading voltage of each point is compared with the voltage read on the memory point of the reference column belonging to the same line.
- This column write and read mechanism significantly reduces the memory cycle time.
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Description
La présente invention a pour objet un dispositif magnétique à polarisation de spin et à empilement(s) tri-couche(s) et une mémoire utilisant ce dispositif.The present invention relates to a magnetic device spin polarization and stack (s) tri-layer (s) and a memory using this device.
Elle trouve une application en électronique et notamment dans la réalisation de points mémoire et de mémoire de type MRAM ("Magnetic Random Access Memory" ou mémoire magnétique à accès direct (ou aléatoire)).It finds an application in electronics and in particular in the realization of memory points and memory type MRAM ("Magnetic Random Access Memory" or magnetic memory direct access (or random)).
Les mémoires magnétiques MRAM ont connu un regain d'intérêt avec la mise au point de jonctions tunnel magnétiques (en abrégé MTJ pour "Magnetic Tunnel Junction") présentant une forte magnétorésistance à température ambiante. Les
La jonction porte la référence 2. Il s'agit d'un empilement comprenant une couche d'oxyde en sandwich entre deux couches magnétiques. Ce système fonctionne comme une vanne de spin, à la différence que le courant circule perpendiculairement aux plans des couches. L'une des couches magnétiques est dite "libre" car son aimantation peut s'orienter dans un champ magnétique extérieur (flèche bidirectionnelle) ; l'autre est dite "piégée" car sa direction d'aimantation est fixée par une couche d'échange antiferromagnétique (flèche unidirectionnelle). Lorsque les aimantations des couches magnétiques sont antiparallèles, la résistance de la jonction est élevée ; lorsque les aimantations sont parallèles, la résistance devient faible. La variation relative de résistance entre ces deux états peut atteindre 40% par un choix approprié des matériaux.The junction bears the
La jonction 2 est placée entre un transistor de commutation 4 et une ligne d'amenée de courant 6. Un courant passant dans celle-ci produit un champ magnétique 7. Un conducteur 8, orthogonal à la ligne d'amenée de courant 6 (c'est-à-dire en l'espèce, perpendiculaire au plan de la figure) permet de produire un second champ magnétique 9 (situé dans le plan de la figure).The
Dans le mode "écriture" (
Dans le mode "lecture" (
Un tel mécanisme d'écriture présente des inconvénients en particulier dans un réseau de jonctions :
- 1) Comme le renversement de l'aimantation de la couche libre d'une jonction se produit sous l'effet de champs extérieurs, et comme les champs de retournement sont statistiquement distribués, il n'est pas impossible de retourner accidentellement certaines jonctions voisines simplement par l'effet du champ magnétique produit le long de la ligne d'adressage 6. Comme, pour des mémoires à haute densité, la taille des points mémoires est nettement submicronique, le nombre d'erreurs d'adressage augmente.
- 2) La diminution de la taille des points mémoires entraîne une augmentation de la valeur du champ de retournement individuel ; un courant plus important est alors nécessaire pour écrire les points mémoires, ce qui tend à augmenter la consommation électrique.
- 3) L'écriture nécessitant deux lignes de courant à 90°, la densité d'intégration se trouve limitée par la présence de ces lignes.
- 4) Le mode d'écriture utilisé ne permet d'écrire qu'un seul point mémoire à la fois, si l'on veut minimiser le risque d'erreur d'adressage.
- 1) As the reversal of the magnetization of the free layer of a junction occurs under the effect of external fields, and as the turning fields are statistically distributed, it is not impossible to accidentally return some neighboring junctions simply by the effect of the magnetic field produced along the address line 6. As, for high-density memories, the size of the memory points is clearly submicron, the number of addressing errors increases.
- 2) The decrease in the size of the memory points results in an increase in the value of the individual reversal field; a larger current is then required to write the memory points, which tends to increase the power consumption.
- 3) Since the writing requires two 90 ° current lines, the integration density is limited by the presence of these lines.
- 4) The write mode used allows only one memory point to be written at a time, in order to minimize the risk of an error in addressing.
Récemment sont apparus d'autres types de dispositifs magnétiques où le reversement de l'aimantation se produit non plus par des champs magnétiques extérieurs mais par des électrons traversant l'empilement perpendiculairement au plan des couches. Ces dispositifs sont décrits dans le document
- a) la résistance du dispositif est si faible qu'il faut injecter un courant très intense pour avoir une tension aux bornes comparable à celle des systèmes anciens,
- b) une telle intensité nécessite un transistor de grande taille, ce qui limite la densité d'intégration de la mémoire,
- c) l'amplitude de la variation de résistance obtenue est très faible (2-3%), ce qui limite la tension de sortie,
- d) dans l'application aux MRAM, le document cité prévoit trois niveaux de conducteurs et deux sources de tension. Un conducteur central a pour but de récupérer le courant polarisé ayant servi au retournement de la couche libre. Le dispositif est donc complexe.
- a) the resistance of the device is so low that it is necessary to inject a very intense current to have a terminal voltage comparable to that of the old systems,
- b) such an intensity requires a large transistor, which limits the integration density of the memory,
- c) the amplitude of the resistance variation obtained is very small (2-3%), which limits the output voltage,
- d) in the application to MRAMs, the cited document provides for three levels of conductors and two sources of voltage. A central conductor aims to recover the polarized current used to turn the free layer. The device is therefore complex.
La présente invention a justement pour but de remédier à ces inconvénients.The present invention precisely aims to overcome these disadvantages.
L'invention vise à réduire la densité critique de courant à partir de laquelle le retournement de l'aimantation se produit dans la couche libre. Les travaux et réflexions du Demandeur ont permis de comprendre que cette densité critique était liée au champ démagnétisant propre à la couche libre. L'invention propose alors un dispositif dans lequel ce champ démagnétisant est très faible, voire nul. Pour cela, on utilise un empilement à trois couches (que l'on appellera par la suite "empilement tri-couche" ou simplement "tri-couche") formé de deux couches magnétiques séparées par une couche conductrice non magnétique, cette dernière ayant une épaisseur suffisamment faible pour que le couplage entre les deux couches magnétiques soit suffisamment fort pour que les aimantations dans ces couches soient antiparallèles. Globalement, un tel système ne présente pas (ou peu) de champ démagnétisant. Le Demandeur qualifie de tels empilements de "synthétiques".The invention aims to reduce the critical current density from which the reversal of magnetization occurs in the free layer. The work and reflections of the Applicant made it possible to understand that this critical density was linked to the demagnetizing field specific to the free layer. The invention then proposes a device in which this demagnetizing field is very weak or even zero. For this purpose, a three-layer stack (hereinafter referred to as a "tri-layer stack" or simply a "tri-layer" layer) formed of two magnetic layers separated by a non-magnetic conductive layer is used. thickness sufficiently low that the coupling between the two magnetic layers is strong enough that the magnetizations in these layers are antiparallel. Overall, such a system does not present (or little) demagnetizing field. The Applicant qualifies such stacks as "synthetic".
De façon précise, l'invention a donc pour objet un dispositif magnétique conforme à la revendication 1.Precisely, the invention therefore relates to a magnetic device according to
Dans un mode de réalisation, la couche piégée est, elle aussi constituée d'un empilement tri-couche, ce deuxième empilement étant recouvert d'une couche d'échange antiferromagnétique fixant la direction des aimantations dans ledit deuxième empilement tri-couche.In one embodiment, the trapped layer is also constituted by a tri-layer stack, this second stack being covered with an antiferromagnetic exchange layer fixing the direction of the magnetizations in said second tri-layer stack.
Dans un autre mode de réalisation, le dispositif comprend un troisième empilement tri-couche séparé du premier par une couche conductrice non magnétique, ce troisième empilement tri-couche reposant sur une seconde couche d'échange antiferromagnétique fixant les aimantations dans ce troisième tri-couche.In another embodiment, the device comprises a third tri-layer stack separated from the first by a non-magnetic conductive layer, this third tri-layer stack resting on a second antiferromagnetic exchange layer fixing the magnetizations in this third tri-layer .
Le matériau des couches magnétiques du premier et/ou du deuxième et/ou du troisième empilement tricouche est de préférence en un matériau pris dans le groupe constitué par Co, Fe, Ni et leurs alliages.The material of the magnetic layers of the first and / or second and / or the third stack The trilayer is preferably of a material selected from the group consisting of Co, Fe, Ni and their alloys.
La couche conductrice non magnétique du premier et/ou du deuxième et/ou du troisième empilement tricouche est de préférence en un métal pris dans le groupe constitué par Ru, Re, Cu, Cr, Pt, Ag.The non-magnetic conductive layer of the first and / or second and / or third trilayer stack is preferably a metal selected from the group consisting of Ru, Re, Cu, Cr, Pt, Ag.
La première et/ou la seconde couche antiferromagnétique peut être en alliage à base de Mn (par exemple FeMn, IrMn, NiMn, PtMn, PtPdMn, RuRhMn).The first and / or second antiferromagnetic layer may be an Mn-based alloy (for example FeMn, IrMn, NiMn, PtMn, PtPdMn, RuRhMn).
-
les
figures 1A et 1B , déjà décrites, montrent un dispositif connu pour l'écriture et la lecture d'une information binaire dans une jonction magnétique à effet tunnel par des champs magnétiques extérieurs ;theFigures 1A and 1B , already described, show a known device for writing and reading a binary information in a tunnel magnetic junction by external magnetic fields; -
la
figure 2 montre, en coupe, un premier mode de réalisation d'un dispositif selon l'invention ;thefigure 2 shows, in section, a first embodiment of a device according to the invention; - les figures 3A et 3B montrent les orientations des aimantations dans les différentes couches selon qu'on a écrit un "0" ou un "1" pour ce premier mode de réalisation ;FIGS. 3A and 3B show the orientations of the magnetizations in the different layers according to whether a "0" or "1" has been written for this first embodiment;
-
les
figures 4A et 4B montrent les variations transitoires de la composante de l'aimantation selon un axe Oz perpendiculaire au plan des couches et selon un axe Oy parallèle au plan des couches, pour une faible et une forte anisotropie ;theFigures 4A and 4B show the transient variations of the magnetization component along an axis Oz perpendicular to the plane of the layers and along an axis Oy parallel to the plane of the layers, for a weak and a strong anisotropy; -
la
figure 5 montre, en coupe, un second mode de réalisation d'un dispositif selon l'invention ;thefigure 5 shows, in section, a second embodiment of a device according to the invention; -
les
figures 6A et 6B montrent les orientations des aimantations dans les différentes couches selon qu'on a écrit un "O" ou un "1", pour ce second mode de réalisation ;theFigures 6A and 6B show the orientations of the magnetizations in the different layers according to whether an "O" or a "1" has been written, for this second embodiment; -
la
figure 7 montre schématiquement une mémoire utilisant une matrice de dispositifs selon l'invention.thefigure 7 schematically shows a memory using a matrix of devices according to the invention.
A propos du phénomène de polarisation de spin pour des électrons circulant dans des dispositifs à jonction tunnel, on peut rappeler les principes suivants. Un courant électrique circulant dans un conducteur est constitué d'électrons dont le spin n'a aucune raison a priori d'être orienté dans une direction particulière. Lorsque ce courant traverse une couche magnétique présentant une aimantation particulière, les spins vont se trouver orientés par des phénomènes d'échange de moment magnétique, de sorte que les électrons sortiront de cette couche avec un spin polarisé. Une telle couche (ou un ensemble de telles couches) constitue ainsi un "polariseur". Ce phénomène peut jouer aussi bien en transmission (à travers la couche) qu'en réflexion (sur cette couche), selon la direction de circulation du courant. Il peut également jouer en sens inverse en laissant passer de préférence des électrons ayant un spin polarisé dans une certaine direction. La fonction de la couche est alors celle d'un analyseur.With regard to the spin polarization phenomenon for electrons circulating in tunnel junction devices, the following principles can be recalled. An electric current flowing in a conductor consists of electrons whose spin has no reason a priori to be oriented in a particular direction. When this current passes through a magnetic layer having a particular magnetization, the spins will be oriented by magnetic moment exchange phenomena, so that the electrons will emerge from this layer with a polarized spin. Such a layer (or a set of such layers) thus constitutes a "polarizer". This phenomenon can play both in transmission (through the layer) and in reflection (on this layer), depending on the flow direction of the current. It can also act in the opposite direction by preferably passing electrons having a polarized spin in a certain direction. The function of the layer is that of an analyzer.
S'agissant maintenant du premier mode de réalisation de l'invention, il consiste à utiliser une jonction tunnel formée de deux empilements tri-couches disposés de part et d'autre d'une couche isolante, par exemple en alumine (Al2O3). Un des tri-couches a sa direction d'aimantation fixée par couplage d'échange avec une couche antiferromagnétique. Cette couche joue un double rôle de polariseur (à l'écriture) et d'analyseur (à l'écriture et la lecture). Le choix d'un tri-couche a été retenu pour éliminer le couplage magnétostatique avec le second tri-couche et donc pour pouvoir utiliser la mémoire sans champ extérieur de compensation. L'autre tri-couche est libre de s'orienter dans la direction de polarisation des spins.. Cette couche possède une anisotropie planaire définissant un axe de facile et un axe de difficile aimantation afin de réduire le temps d'écriture. Les épaisseurs des couches magnétiques de ce système tri-couche sont quasiment égales afin d'éliminer l'effet de champ démagnétisant et donc permettre l'aimantation de cette couche de précessionner facilement hors du plan.Turning now to the first embodiment of the invention, it consists in using a tunnel junction formed of two tri-layer stacks disposed on either side of an insulating layer, for example alumina (Al 2 O 3 ). One of the three-layers has its magnetization direction fixed by exchange coupling with an antiferromagnetic layer. This layer plays a dual role of polarizer (writing) and parser (writing and reading). The choice of a tri-layer was chosen to eliminate the magnetostatic coupling with the second tri-layer and thus to be able to use the memory without an external compensating field. The other tri-layer is free to orient itself in the spin polarization direction. This layer has a planar anisotropy defining an easy axis and a hard magnetization axis in order to reduce the write time. The thicknesses of the magnetic layers of this tri-layer system are almost equal in order to eliminate the demagnetizing field effect and thus allow the magnetization of this layer to precede easily out of the plane.
Dans le mode écriture, un courant de densité supérieure à la densité critique traversant la jonction va provoquer une précession et un alignement de l'aimantation de la couche libre (la plus proche de la barrière d'oxyde) par transfert du moment magnétique des électrons polarisés au moment magnétique de la couche libre. La tension apparaissant aux bornes de la jonction, permet de suivre l'état magnétique de la couche libre. L'écriture peut se faire en courant continu ou en courant pulsé, la durée de l'impulsion devant être ajustée en fonction du processus de retournement de l'aimantation.In the write mode, a current of density greater than the critical density crossing the junction will cause precession and alignment of the magnetization of the free layer (closest to the oxide barrier) by transfer of the magnetic moment of the electrons polarized at the magnetic moment of the free layer. The voltage appearing at the terminals of the junction makes it possible to follow the magnetic state of the free layer. The writing can be done in direct current or in pulsed current, the duration of the pulse to be adjusted according to the process of reversal of the magnetization.
Dans le mode lecture, un courant de densité inférieure à la densité critique traverse la jonction et permet de lire l'état magnétique du dispositif, lequel se comporte ainsi comme un point mémoire.In the read mode, a current of density less than the critical density crosses the junction and makes it possible to read the magnetic state of the device, which thus behaves like a memory point.
La
Selon le mode de réalisation illustré, la couche piégée 12 est un tri-couche composé de deux couches magnétiques 121, 123 séparées par une couche conductrice non magnétique 122. De même, la couche libre 16 est un tri-couche composé de deux couches magnétiques 161, 163 séparées par une couche conductrice non magnétique 162.According to the illustrated embodiment, the trapped
Dans les deux tri-couches 12 et 16, les aimantations des deux couches magnétiques sont antiparallèles, comme représenté symboliquement sur la figure par les flèches de directions alternées, flèches qui représentent l'aimantation. Cet antiparallélisme est dû à un couplage antiferromagnétique très fort existant entre les couches magnétiques. Les épaisseurs des couches magnétiques 121, 123 sont avantageusement les mêmes afin d'avoir un couplage magnétostatique nul sur la couche libre 16.In the two tri-layers 12 and 16, the magnetizations of the two magnetic layers are antiparallel, as represented symbolically in the figure by the arrows of alternating directions, arrows which represent the magnetization. This antiparallelism is due to a very strong antiferromagnetic coupling existing between the magnetic layers. The thicknesses of the
La couche libre 16 a des caractéristiques similaires à la couche piégée 12. Cependant, n'étant pas piégée par échange, elle est libre, et voit la direction de son aimantation changer lorsqu'un courant polarisé en spin la traverse. Ce changement est lié au transfert de moment magnétique des électrons vers l'aimantation de la couche.The
La barrière 14 est formée préférentiellement d'une couche d'aluminium oxydée ou nitrurée, et elle est obtenue par des méthodes connues de l'homme de l'art (oxydation par plasma, oxydation naturelle in situ, source d'oxygène atomique, ...). Des matériaux semi-conducteurs peuvent aussi être employés mais les propriétés magnétorésistives ne sont pas aussi bonnes qu'avec les nitrures et oxydes.The
La figure 3A permet d'illustrer l'écriture d'un "O" et la figure 3B l'écriture d'un "1". Sur ces figures, on n'a pas représenté l'amenée de courant ni le transistor. Les différentes directions sont repérées par rapport à un trièdre trirectangle Oxyz, la direction Oz étant perpendiculaire au plan des couches. Par ailleurs, la
Pour écrire un "0", on fait circuler dans l'empilement un courant (continu ou pulsé) de signe positif, c'est-à-dire circulant de haut en bas (donc vers le transistor). Les électrons voient leur spin polarisé dans la couche 123 selon la direction (-y). Ils vont transmettre leur moment magnétique aux moments de la couche 161 dont l'aimantation va s'aligner parallèlement à celle de la couche 123. La couche 163, couplée antiparallèlement à la couche 161, va donc aussi se réorienter. Lors du transfert de moment magnétique, l'aimantation de la couche 161 va entrer en précession autour de l'axe (-y) avec une composante Mz qui va osciller au cours du temps, comme le montre la
Comme dit précédemment, l'écriture peut se faire en courant continu ou pulsé. Dans le cas d'un courant pulsé, la durée de l'impulsion doit être suffisamment longue pour que le retournement soit complet. Le contrôle du retournement peut s'effectuer par la mesure de la tension aux bornes de la jonction. Lorsque les aimantations des couches 123 et 161 sont parallèles, la probabilité de transfert des électrons par effet tunnel est grande et la résistance de la jonction est faible. Si le retournement ne s'est pas effectué complètement, la résistance est grande. Par comparaison avec la tension prise aux bornes d'une jonction de référence, on détermine l'état magnétique du dispositif. Dans cette étape de contrôle de l'état magnétique, la couche 123 (fixée par échange) joue le rôle d'analyseur pour sonder l'orientation de la couche libre 161.As said above, the writing can be done in direct current or pulsed. In the case of pulsed current, the duration of the pulse must be long enough for the reversal to be complete. The overturn control can be done by measuring the voltage across the junction. When the magnetizations of the
Pour écrire un "1", on fait circuler un courant de signe négatif comme le montre la figure 3B. En partant de l'état "0", les électrons majoritaires polarisés dans la couche 161 selon (-y) vont traverser la couche 123, alors que les électrons minoritaires polarisés selon (+y) vont s'accumuler devant la couche 123. Ces électrons de spins antiparallèles à la couche 161 vont transférer leur moment magnétique aux moments de la couche 41 et provoquer une précession jusqu'au retournement de l'aimantation de la couche 161 comme montré sur la figure 3B. Cette configuration magnétique correspond à l'écriture d'un "1" et la résistance de la jonction est maximum.To write a "1", a current of negative sign is circulated as shown in FIG. 3B. Starting from the state "0", the polarized majority electrons in the
Pour la lecture, on envoie un courant dont la densité est inférieure à la densité critique et on compare la tension de sortie à la tension d'une jonction de référence, afin de déterminer l'état magnétique du dispositif.For reading, a current whose density is less than the critical density is sent and the output voltage is compared with the voltage of a reference junction, in order to determine the magnetic state of the device.
Dans un second mode de réalisation, le dispositif comprend trois tri-couches, deux des tri-couches étant disposés de part et d'autre d'une couche isolante, par exemple en alumine (Al2O3). L'un de ces tri-couches a ses directions d'aimantation fixées par couplage d'échange avec une couche antiferromagnétique. Cette couche joue un double rôle de polariseur (à l'écriture) et d'analyseur (à l'écriture et la lecture). Le choix d'un tri-couche permet d'éliminer le couplage magnétostatique sur le second tri-couche et donc de pouvoir utiliser la mémoire sans champ extérieur de compensation. L'autre tri-couche est libre de s'orienter dans la direction de polarisation des spins. Cette couche peut posséder une anisotropie planaire définissant un axe de facile et un axe de difficile aimantation afin de réduire le temps d'écriture. Les épaisseurs des couches magnétiques de ce système sont quasiment égales afin d'éliminer l'effet de champ démagnétisant. Le dispositif comprend encore un polariseur séparé de la jonction tunnel par une couche conductrice non magnétique et formé préférentiellement d'un empilement tri-couche piégé par échange avec une couche antiferromagnétique afin de maintenir sa direction d'aimantation.In a second embodiment, the device comprises three tri-layers, two of the tri-layers being disposed on either side of an insulating layer, by example alumina (Al 2 O 3 ). One of these tri-layers has its magnetization directions fixed by exchange coupling with an antiferromagnetic layer. This layer plays a dual role of polarizer (writing) and parser (writing and reading). The choice of a tri-layer makes it possible to eliminate the magnetostatic coupling on the second tri-layer and thus to be able to use the memory without an external compensating field. The other tri-layer is free to orient itself in the direction of polarization of the spins. This layer may have a planar anisotropy defining an easy axis and a hard magnetization axis in order to reduce the write time. The thicknesses of the magnetic layers of this system are almost equal in order to eliminate the demagnetizing field effect. The device also comprises a polarizer separated from the tunnel junction by a non-magnetic conductive layer and preferably formed of a tri-layer stack trapped by exchange with an antiferromagnetic layer in order to maintain its direction of magnetization.
La
La couche 30 séparant le premier et le troisième tri-couches peut être formée à partir d'un métal noble. Son épaisseur est choisie entre 3 et 10 nm pour éviter des couplages magnétiques intempestifs entre les tri-couches 16 et 32.The
L'écriture des états magnétiques "1" et "O" s'effectue, comme précédemment, par le choix de l'orientation du sens du courant comme le montrent les
Pour l'écriture d'un "1", les rôles des polariseurs sont inversés, mais les effets de stabilisation et d'abaissement de la densité critique demeurent.For the writing of a "1", the roles of the polarizers are reversed, but the stabilizing and lowering effects of the critical density remain.
Le polariseur 32 élimine le champ de couplage magnéto-statique sur la couche 16 et permet aussi d'avoir une direction d'échange identique entre les couches 121 et 323 afin de rendre possible la mise en ordre magnétique des couches antiferromagnétiques d'échange 10 et 34. Il est en effet difficile de définir deux directions d'échange opposées dans un système utilisant un seul type de matériau antiferromagnétique.The
La lecture s'effectue comme dans la première variante en injectant un courant de densité inférieure à la densité critique et en comparant la tension lue à la tension d'une jonction de référence.The reading is performed as in the first variant by injecting a current of density less than the critical density and comparing the voltage read to the voltage of a reference junction.
Les deux modes de réalisation qui viennent d'être décrits peuvent être comparés dans le tableau ci-dessous, où :
- t est l'épaisseur de la couche magnétique à retourner,
- Ms est l'aimantation à saturation de la couche à retourner, dans le cas de CoFe (Ms=1500 emu/cc)),
- Hk est l'anisotropie de la couche magnétique à retourner,
- Jc (écriture) est la densité de courant pour écrire un point mémoire,
- RAmax est le produit de la résistance par la surface de la jonction tunnel, défini de telle façon que la tension à l'écriture n'excède pas 0,6 V,
- Jc (lecture) est la densité de courant pour une tension
de lecture de 0,3 V avec RAmax, - amin est la taille minimale d'un côté du point mémoire (pour un point mémoire carré) avant d'atteindre la limite superparamagnétique.
- t is the thickness of the magnetic layer to be returned,
- Ms is the saturation magnetization of the layer to be returned, in the case of CoFe (Ms = 1500 emu / cc),
- Hk is the anisotropy of the magnetic layer to be returned,
- Jc (write) is the current density to write a memory point,
- RA max is the product of the resistance of the tunnel junction surface, defined in such a way that the write voltage does not exceed 0.6 V,
- Jc (reading) is the current density for a reading voltage of 0.3 V with RA max ,
- a min is the minimum size of one side of the memory point (for a square memory point) before reaching the superparamagnetic limit.
La valeur de amin est calculée d'après la formule :
dans laquelle la valeur 84 est calculée en considérant une durée de fonctionnement de la mémoire de 100 ans à une température de 100°C.
wherein the value 84 is calculated considering a running time of the 100-year memory at a temperature of 100 ° C.
On voit, d'après ce tableau, qu'avec l'invention on peut atteindre de faibles densités de courant d'écriture, compatibles avec des jonctions de produit RA raisonnables (>100 Ω.µm2). De tels produits RA peuvent être obtenus, soit par oxydation plasma, soit et de préférence par oxydation naturelle in situ.It can be seen from this table that with the invention it is possible to achieve low write current densities compatible with reasonable RA product junctions (> 100 Ω.μm 2 ). Such RA products can be obtained either by plasma oxidation or, preferably, by natural oxidation in situ.
La
Lorsqu'une séquence de bits doit être écrite (par exemple 100110), on commande l'adressage d'une colonne par une impulsion apte à ouvrir les transistors de la colonne en question et l'on envoie sur chaque ligne une impulsion de courant ayant une polarité appropriée (dans l'exemple pris respectivement +--++-). Tous les bits se trouvent ainsi écrits dans la colonne de cette mémoire, simultanément.When a sequence of bits has to be written (for example 100110), the addressing of a column is controlled by a pulse able to open the transistors of the column in question and a current pulse is sent on each line having an appropriate polarity (in the example taken respectively + - ++ -). All the bits are thus written in the column of this memory, simultaneously.
Cet adressage multiple est possible grâce à l'invention puisque, comme expliqué dans l'introduction, un point mémoire peut être écrit sans risque d'écriture intempestive sur les points voisins.This multiple addressing is possible thanks to the invention since, as explained in the introduction, a memory point can be written without risk of inadvertent writing on neighboring points.
Quelque part dans la mémoire, par exemple au centre, se trouve une colonne de référence 100, qui permet la lecture. Lorsqu'un courant de lecture circule dans les points mémoires d'une colonne 90, on compare la tension de lecture de chaque point avec la tension lue sur le point mémoire de la colonne de référence appartenant à la même ligne.Somewhere in the memory, for example in the center, is a
Ce mécanisme d'écriture et de lecture par colonne réduit considérablement le temps de cycle de la mémoire.This column write and read mechanism significantly reduces the memory cycle time.
Claims (11)
- Magnetic device consisting of:• a first magnetic layer called the "anchored" layer (12) which has a fixed magnetisation direction,• a second magnetic layer called the "free" layer (16) which has a variable magnetisation direction,• an insulating or semiconducting layer (14) which separates the anchored layer from the free layer,• means (22, 24) for passing a current of electrons through and perpendicular to the layers,• the anchored magnetic layer or the free magnetic layer being able to polarize the spin of said electronics,the free magnetic layer (16), at least, consisting of a first tri-layer stack which consists of two magnetic layers (161, 163) with anti-parallel magnetisation, separated by a conducting non-magnetic layer (162), characterized in that the means (22, 24) for passing into the layers and perpendicular thereto an electron current are writing means making an electron current pass through the layers in a first direction and in the opposite direction.
- Device in accordance with claim 1, in which the said anchored magnetic layer (12) consists of a second tri-layer stack which consists of two magnetic layers (121, 123) with anti-parallel magnetisation, separated by a conducting non-magnetic layer (122), this second stack being covered with a first layer of anti-ferromagnetic exchange (10) which fixes the direction of magnetisation in the said second tri-layer stack (12).
- Device in accordance with claim 2, including additionally a third tri-layer stack (32) formed of two magnetic layers (321, 323) with anti-parallel magnetisation, separated by a conducting non-magnetic layer (322), this third stack (32) being separated from the first (16) by a conducting non-magnetic layer (30), this third tri-layer stack (32) being mounted on a second anti-ferromagnetic exchange layer (34) which fixes the magnetisation in the said third tri-layer stack (32).
- Device in accordance with any of claims 1 to 3, in which the two magnetic layers (161, 163), in the first tri-layer stack (16) are of the same thickness.
- Device in accordance with any of claims 1 to 3, in which the magnetic layers of the first tri-layer stack (16) and/or the second tri-layer stack (12) and/or the third tri-layer stack (32) are made from a material taken from the group formed by Co, Fe, Ni and their alloys.
- Device in accordance with any of claims 1 to 3, in which the conducting non-magnetic layer of the first tri-layer stack (162), and/or the second tri-layer stack (122) and/or the third tri-layer stack (322) is made from a metal taken from the group formed by Ru, Re, Cu, Cr, Pt, Ag.
- Device in accordance with either of claims 2 and 3, in which the first anti-ferromagnetic layer (10) and/or the second anti-ferromagnetic layer (34) is made from a Mn-based alloy.
- Device in accordance with any of claims 1 to 7, wherein the current of electrons has a density greater than a certain critical density.
- Device in accordance with claim 8, including additionally reading means suitable for passing a current of electrons through the layers, with a density less than the said critical density, and means for measuring the voltage appearing at the terminals of the layer stack terminals.
- Memory consisting of a matrix of memory cells addressable in rows (80) and columns (90), characterized in that each memory cell consists of a magnetic device (60) in accordance with any of claims 1 to 7, and by a current switching means (70) connected in series with the device (60), each magnetic device (60) being connected to an addressing row (80) and each switching means (70) to an addressing column (90).
- Memory in accordance with claim 10, including additionally a reference column (100) and means for comparing the voltage read at the terminals of a device located at the intersection between a specific row (80) and a column (90), and the voltage read at the terminals of the device located on the same row (80) but in the reference column (100).
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0015895A FR2817999B1 (en) | 2000-12-07 | 2000-12-07 | MAGNETIC DEVICE WITH POLARIZATION OF SPIN AND A STRIP (S) TRI-LAYER (S) AND MEMORY USING THE DEVICE |
FR0015895 | 2000-12-07 |
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JP2009239317A (en) | 2009-10-15 |
JP5148566B2 (en) | 2013-02-20 |
EP1223585A1 (en) | 2002-07-17 |
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